Papers by Keyword: Atomic-Scale

Abstract: nterdiffusion in the Cu|Cu30Zn diffusion couples under a strong gravitational field was investigated at 400. The Cu-Brass diffusion couples were prepared by electrolytic plating method. Two samples were centrifuged at 0.4×10⁶ G for 60 hours. The initial contact interface was perpendicular to the gravitational force direction. The two different orientations of the samples were studied: with Cu 1) downside and 2) upside of the gravitational force direction. It was found that interdiffusion was markedly affected by the gravity field. This was caused by the sedimentation of atoms where heavy Cu atoms move in the direction of the strong gravitational field. A numerical simulation of the sedimentation process is self-consistent with experimental results.

Abstract: The growth of nano CVD diamond films on low index faces such as (111) face and (100) face under different proposed surface chemical reaction model was simulated by using Kinetic Monte Carlo (KMC) method from atomic scale. The results, for example the influence of deposition time t, substrate temperature T_s, and atomic hydrogen concentration [H] on the film deposition rate, surface roughness, and H embedded in the film under different processing conditions, were systematically analyzed and compared. And the adsorption of various species on {111}-oriented diamond cluster was preliminarily computed from electronic scale by Local Density Approximation (LDA) method to assist understanding the surface adsorption mechanism. It is indicated that the film morphology and quality obtained from atomic scale KMC simulation varies according to the chemical reaction models. And our initial electronic scale computation on {111}-oriented diamond cluster showed that single-carbon species can be adsorbed on the activated site more easily than double-carbon species and the former will result in a more stable state than the latter. In order to reveal the nano CVD diamond film growth mechanism, more work about various species adsorption on many different morphological CVD diamond surfaces is needed.

Abstract: Nanowires and nanofilms are fundamental building blocks of micro and nano-electronics for both of bottom-up and top-down technologies. Monitoring and recording the mechanical property dynamics at atomic scale are important to understand the atomic mechanism of new and surprising nano-phenomena and design new applications. Through years’ endeavors, we developed tensile and/or bending in-situ atomic-lattice resolution electron microscopy methods and equipments for nanowires and successfully conducted atomic-lattice resolution mechanical tests on individual nano-objects. With this, we observed the brittle materials SiC and Si nanowires (NWs) become highly ductile at room temperature. The crystalline structural evolution processes corresponding to the occurrence of unusual large strain plasticity includes the dislocation initiation, dislocation accumulation and amorphorization as well as the necking of the one dimensional nanowires were fully recorded at atomic scale and in real time. We also expand the experimental methods and equipments to two-dimensional nanofilms. An example of tensile experiment on nano-crystalline Au films is presented. The deformation mechanisms of nano-crystalline gold films were observed at the atomic scale and real-time. At the mean time, an atomic scale the crack blunting behavior was captured and the plastic deformation mechanism of the single nano-crystalline was revealed.